Cyclopentadienyl carbonyls



United States Patent Ofifice 3,026,344 Patented Mar. 20, 1962 3,026,344 CYCLOPENTADIENYL CARBONYLS William J. Craven, Elizabeth, and Herbert K. Wiese,

Cranford, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Oct. 29, 1958, Ser. No. 770,303 9 Claims. (Cl. 260-439) This invention relates to a novel process for the preparation of cyclopentadienyl cobalt carbonyl including hydrocarbon-substituted cyclopentadienyl cobalt carbonyl compounds. More specifically, this invention relates to the preparation of the aforesaid cyclopentadienyl cobalt carbonyl compounds by a single step process.

Oyclopentadienyl and substituted cyclopentadienyl cobalt carbonyls of this invention are known to have antiknock qualities and are useful as gasoline additives. They are also useful as oil-soluble oxo catalysts. For simplification, the term a cyclopentadiene compound will be employed to include a hydrocarbon-substituted cyclopentadiene and dimers thereof. The term cyclopentadiene cobalt carbony is also intended to include the hydrocarbon-substituted cyclopentadiene cobalt carbonyl compounds, i.e. CpCo(CO) where Cp is any cyclopentadiene compound.

In accordance with the prior art, the preparation of cyclopentadienyl cobalt carbonyl involved several steps. It was first necessary to produce the sodium cyclopentadienyl compound which was then reacted with a neutral cobalt salt to form the cyclopentadienyl cobalt salt, which in turn was reacted with carbon monoxide to yield the desired cyclopentadienyl cobalt carbonyl. While this process is satisfactory for the production of these cobalt carbonyl compounds, the required three stages have obvious economic drawbacks with regard to commercial application.

It has now been discovered that cyclopentadiene, hydrocarbon-substituted cyclopentadiene, or their dimers may be reacted with cobalt comprising material at elevated temperatures under carbon monoxide pressures to effect the direct production of the desired cyclopentadienyl cobalt carbonyl compounds.

The following general formula represents the class of cyclopentadiene compounds suitable as reactants for the present process:

or dimers thereof wherein each of the Rs represent the same or difierent radicals selected from the group consisting of hydrogen and hydrocarbon radicals. As examples of various compounds coming within the scope of the above formula, there are Z-methyl cyclopentadiene, 2-ethyl cyclopentadiene, 2-isopropyl cyclopentadiene, 1,4-dimethyl cyclopentadiene, l-methyl-4-ethyl cyclopentadiene, l,2,3,4-tetramethyl cyclopentadiene, 2-tertiary butyl cyclopentadiene, 2-isopropenyl cyclopentadiene, 1-hexyl-2-(2-phenyl propyl) cyclopentadiene, 2-phenyl cyclopentadiene, 3,4-dicyclopropyl cyclopentadiene, 2-tolyl cyclopentadiene, phenyl-butyl cyclopentadiene, l-methyl cyclopentadiene and l-butyl cyclopentadiene and similar hydrocarbonsubstituted cyclopentadienes. The particular hydrocarbon substituent is not of critical importance with regard to the operability of the present process since the hydrocarbon substituents do not interfere with the principal reaction; however, preferred reactants are the C C alkyl cyclopentadienes and/ or their dimers.

To obtain the dimer of the cyclopentadiene compound from the monomer, any well-known technique such as heat soaking the monomer at elevated temperatures, e.g. 50 to 210 C. for a period of several hours may be employed.

As the cobalt containing reactant, there may be employed any cobalt compound such as oil soluble fatty acid salts of cobalt, inorganic salts, metallic cobalt preferably where the surface has been activated or, if desired, preformed cobalt carbonyl. Thus, for example, there can be employed the salts of cobalt and higher molecular weight fatty acids such as stearic, oleic, naphthenic, linoleic and the like. Water soluble salts of organic acids may include cobalt acetate, cobalt formate and the like. As inorganic salts, there may be employed cobalt chloride, cobalt bromide, cobalt iodide, cobalt sulfide and oxides such as cobaltous and cobaltic oxides. When employing a cobalt halide or sulfide, it may be desirable to use a halogen acceptor such as metallic copper. By the term cobalt carbonyl it is intended to include such compounds as Co (CO) H[Co(CO) and [Co(CO) To obtain an active metallic cobalt having a surface substantially free of oxides, sulfides and the like, cobalt salts such as cobalt oxalate may be decomposed to form cobalt oxide at temperatures of 125 to 250 C. and the cobalt oxide reduced with hydrogen at elevated temperatures of, for example, 300 C. to obtain the active metallic cobalt. Another technique for obtaining metallic cobalt having an active surface is to treat a cobalt-aluminum alloy with aqueous sodium hydroxide to dissolve away the aluminum leaving highly active metallic cobalt. It is evident, therefore, that cobalt in almost any form may be employed for the reaction of this invention since under reaction conditions, if cobalt carbonyl is not employed, it will be formed in situ from any cobalt containing compound.

As the carbon monoxide containing gas, it is preferred to employ essentially pure carbon monoxide; however, impure gases may be utilized as long as the impurities do not interfere with the principal reactant. For example, a hydrogen'containing carbon monoxide gas may be employed if a hydrogen deficient component is utilized in the reaction mixture to absorb the hydrogen and thereby avoid substantial hydrogenation of the cyclopentadiene reactant. A hydrocarbon reactant is preferably employed to absorb any hydrogen formed in the reaction. This hydrocarbon may be the cyclopentadiene compound itself or some olefin, such as hexene, pentene, octene, cyclohexene and others. Although the use of a large excess of a cyclopentadiene compound to absorb any hydrogen formed in the reaction is not detrimental to the reaction, it is generally undesirable from a standpoint of product work-up. Generally the cyclopentadiene cobalt carbonyl products boil close to the dimers or hydrogenated dimers of the cyclopentadiene compounds, thus making the purification of the products difiicult. While the stoichiometric reaction requires one mole of the cyclopentadiene dimer or two moles of the cyclopentadiene monomer for two moles of cobalt compound, it is preferred to employ a ratio of cobalt to cyclopentadiene monomer ranging from 1/3 to 3/1. If desired, a hydrocarbon solvent may be employed in a volume ratio of 1/10 to 10/1. The solvent may comprise any olefin, particularly an olefin capable of reacting with any hydrogen formed in the reaction, benzene, toluene, xylene, heptane and others.

Temperatures for the reaction vary between -300 C. and even this range may be exceeded on either end to obtain the desired results. Carbon monoxide pressure may be maintained between 500 and 10,000 p.s.i.g. In general, the higher carbon monoxide pressures permit a faster reaction rate with higher conversions and yields for a given period of time. Good contact between the carbon monoxide gas and liquid reactants in accordance with known techniques is desirable for optimum results,

vent.

although the process is operable by merely pressuring a reactor, containing the cobalt and cyclopentadiene reactant, with carbon monoxide gas.

The cyclopentadiene cobalt carbonyls are distillable under reduced pressure from the reaction mixture and may be stored for appreciable periods of time in an inert atmosphere. If some unconverted cyclopentadiene dimer distills over With the cyclopentadienyl cobalt carbonyl, other means such as extractive distillation, solvent extraction or fractional crystallization can be employed. If desired, the solution of cyclopentadienyl cobalt carbonyl in hydrocarbons may be used as such as a fuel additive.

The preferred technique of separation, however, involves distillation under reducedpressure ranging from several microns to about 250 mm. To simplify the distillation and thus obtain a high purity product, it is generally important to select the ratio of cobalt/cyclopentadiene compound in the reactor in such a manner as to minimize the amount of unconverted cyclopentadiene compound.

For a clearer understanding of the present invention, reference may be had to the following examples which set forth various processes for the production of cyclopentadienyl cobalt carbonyl compounds.

Example 1 A pressure reactor was charged with 24 grams (0.4 mole) of Raney cobalt metal, 120 grams (0.7 mole) of methylcyclopentadiene dimer and 200 ml. of benzene sol- The mixture was then heated to 210 C. with a gauge reading of 1700 p.s.i.g. carbon monoxide pressure and a temperature was maintained in the closed reactor for a period of about 12 hours. The crude reaction mixture obtained was filtered free of unreacted metal powder and distilled. The fraction boiling at 55-65 C. at 5 mm. pressure was collected and found to contain methylcyclopentadienyl cobalt carbonyl (MCPD Co(CO)- as well as nnreacted methylcyclopentadiene dimer. In-

frared analysis of the distillate showed the characteristic metal-carbonyl absorption peaks at 1960 cm. and 2030 cmf The fraction weighed 33 grams and contained 3.62% cobalt.

Example 2 The conditions of Example 1 are repeated employing 5000 p.s.i.g. to obtain larger yields of methylcyclopentadienyl cobalt carbonyl.

Example 3 Example 4 A pressure reactor was charged with 38.5 grams (0.58 mole) of dicyclopentadiene, 221 grams of cobalt oleate (0.43 mole) and 650 ml. xylene. The mixture was heated to 180190 C. for 8 hours with 3000 p.s.i.g. carbon monoxide. The mixture was then distilled and grams of a dark red liquid boiling between 58 to C. at 20 mm. was collected. The product contained 54 grams of cyclopentadienyl cobalt carbonyl (65% yield).

What is claimed is:

1. A process for the preparation of a cyclopentadienyl cobalt carbonyl which comprises reacting a stoichiometric excess of a cyclopentadiene dimer compound selected from the group consisting of dimers of cyclopentadiene and C C alkyl cyclopentadienes, and dimers thereof with a cobalt containing reactant selected from the group consisting of oil soluble cobalt salts of fatty acids and metallic cobalt under a carbon monoxide pressure of from 500 to 10,000 p.s.i.g. and at a temperature from to 300 C. and wherein said excess is employed as a hydrogen acceptor to absorb hydrogen liberated during the reaction.

2. A process in accordance with claim 1 wherein said compound is di-cyclopentadiene.

3. A process in accordance with claim 1 wherein said compound is di-methylcyclopentadiene.

4. A process for preparing methyl cyclopentadienyl cobalt carbonyl which comprises reacting a stoichiometric excess of di-methylcyclopentadiene with metallic cobalt under a carbon monoxide pressure of from 500 to 10,000 p.s.i.g. and at a temperature of from 100 to 300 C.

5. A process in accordance with claim 1 wherein the cobalt-containing reactant is cobalt oleate.

6. A process in accordance with claim 1 wherein an olefin is employed as the hydrogen acceptor.

7. A process in accordance with claim 1 wherein said compound is the dimer of 2-isobutyl cyclopentadiene.

8. A process for preparing cyclopentadienyl cobalt carbonyl which comprises reacting a stoichiometric excess of dicyclopentadiene with cobalt oleate under a carbon monoxide pressure of from 500 to 10,000 p.s.i.g. and at a temperature of from 100 to 300 C.

9. A process for preparing isobutyl cyclopentadienyl cobalt carbonyl which comprises reacting a stoichiometric excess of 2-isobutyl cyclopentadiene dimer with metallic cobalt under a carbon monoxide pressure of from 500 to 10,000 p.s.i.g. and at a temperature of from 100 to 300 C.

Piper et a1.: J. Inorganic and Nuclear Chemistry, vol. 7

I, pp. -174 1955 Sidgwiclr: Chemical Elements and Their compounds, p. 1422 (1950). 

1. A PROCESS FOR THE PREPARATION OF A CYCLOPENTADIENYL COBALT CARBONYL WHICH COMPRISES REACTING A STOICHIOMETRIC EXCESS OF A CYCLOPENTADIENE DIMER COMPOUND SELECTED FROM THE GROUP CONSISTING OF DIMERS OF CYCLOPENTADIENE AND C0-C8 ALKYL CYCLOPENTADIENES, AND DIMERS THEREOF WITH A COBALT CONTAINING REACTANT SELECTED FROM THE GROUP CONSISTING OF OIL SOLUBLE COBALT SALTS OF FATTY ACIDS AND METALLIC COBALT UNDER A CARBON MONOXIDE PRESSURE OF FROM 500 TO 10,000 P.S.I.G. AND AT A TEMPERATURE FROM 100* TO 300*C. AND WHEREIN SAID EXCESS IS EMPLOYED AS A HYDROGEN ACCEPTOR TO ABSORB HYDROGEN LIBERATED DURING THE REACTION. 